Travelling to UK for tourism with a misdemeanor? Please help

you really should get advice from an attorney....it is unlikely anyone here has the requisite legal education and credentials to do anything more than offer a well meaning opinion/guess about your situation.

No visa is required for US citizens for tourist entry to the UK.

I am a US citizen too.
I have an uncle and family in France too. Maybe I can use a transit Visa?

As David said American citizens don't need a visa to travel to the UK. Just your passport.

It is not a US decision. It is a UK decision and you need to contact a UK embassy or consulate -- like tomorrow. AND -- do not rely on any advice for this site no manner how well intended. Again, if you are a US citizen traveling on an American passport, you do not need any visa, transit, or other wise to travel. So I don't why you keep raising that question.

Check with the UK Embassy. While a US citizen does not need a visa to visit the UK, you may need a visa because of the criminal conviction.

Check this out: https://www.gov.uk/check-uk-visa/y

While it is generally prudent advice to contact a lawyer or the consulate for more information, there are a couple relevant facts:

First, you mention you are a "US Citizen", assuming that means you have US Passport, then as others have said, you show up...show your passport...and they allow you in. Unless you are on a "no fly" list for one country or the other, have an Interpol warrant out for you, or the UK are hunting for you...you will be OK.

What you are describing is a misdemeanor, not a felony, no Government entity outside the US can even see that charge. Now if you are on Probation or other restrictions, then the local authorities may have a problem with you traveling to Europe, but the UK could care less, unless at entry you divulge information.

The quick summary of the legal position is that if the offence was committed more than 12 months ago and was not subject to a custodial sentence that in itself is unlikely to be enough, unless the individual concert is a persistent offender or has caused serious harm. I'm not clear here whether the ultimate outcome amounts to an acquittal after appeal.

The UK makes no distinction between felony and misdemeanour. This was abolished here years ago. For leave to enter the only things that matter is the sentence, how long ago it was, and whether there is a pattern of them.

The USA by the way makes people disclose convictions for entry that in the UK are considered as 'spent', ie you don't have to mention them and they don't show up on normal level criminal records checks.

I’m not a lawyer, but I can’t imagine the typical immigration officer asking about a relatively minor crime. One friend of mine has 4 DUI convictions and was admitted to the UK. I know that admission to Canada can be a concern, but I imagine that information sharing between the USA and Canadian law enforcement is far more prevalent than between the USA and the UK.

Again, not an immigration lawyer but I don’t think I’d be sweating a minor misdemeanor.

I think UK and USA do share information. There is a treaty that was signed in 2013 and enforced in 2014 that requires information-sharing in order to keep criminals out of each other's countries. After much research, it is advisable to be honest with the immigration officer and bring supporting documents that corroborate your charge and reason for being in UK. I may try to enter UK through Dover in April or May 2019 and hopefully will post my experience.

But why wouldn't you just inquire at the UK Embassy now?

You can't just inquire at the UK Consulate in Los Angeles. You need an appointment with a Visa application

The official government UK web site for border protection says "You may wish to apply for a visa if you have a criminal record" even if you are a US citizen traveling with a US passport and would not need a visa otherwise.

So maybe showing up at the consulate with a visa application and an appointment is the best way to go. What's the worst they'll do, tell you are not allowed to travel there? Better to find out now than after paying for a plane ticket and then being turned away at the UK airport.

Exactly, Mark...