14 days in Europe in July

Much of Europe will be getting quite warm in July, and the continent will be packed with tourists. In western Europe, I wouldn't want to go any further south than Lyon or Bordeaux in France, both large cities with things to do and great food. You could also visit Strasbourg or Colmar in eastern France, near Germany, on your way west to London, if your husband insists (warm-hot, packed). In the UK, Bristol, Bath, or Oxford may be less crowded and not as hot as London, or head farther north to York or Edinburgh.
The best area to go in western Europe in July is probably Scandinavia.
Good luck and good travels!

London and York-you can see lots of cathedrals-day trips to Cambridge for Kings College, Salisbury Cathedral near Bath, even York could be day trip
Possibly Wales for castles
Dover castle as day trip from London
Fewer airbnb reservations to make if you stay in London!
or maybe Loire Chateaux and Chartres Cathedral near Paris for a few days

Krakow, Prague and Budapest are near the top of my current bucket list-but I've already spent time in London and environs on 6 different trips with another trip planned for that area next summer

It's true that you're at risk of running into a heat wave in much of Europe in July. Where are you from? At what time of year did you visit Paris and Italy?

July sounds like a good time to visit northern England and Scotland. If you like cities, I had a great visit (in September 2016) to Liverpool, Manchester, and Glasgow. These places will certainly satisfy your cravings for architecture, gardens, and walking tours, and while they're not famous for food, I ate just fine. Here's my trip report: https://community.ricksteves.com/travel-forum/trip-reports/uk-trip-report-glasgow-manchester-liverpool-in-september-2016

Of course, if you prefer smaller towns or villages, northern England and Scotland have those too.

We are from Texas and my husband works outdoors, so heat won't be an issue.

What "parts of Western Europe"? Getting there by train from middle Europe is potentially taxing, so I'd suggest looking into flights.

There's plenty worth seeing in France outside of Paris, if that is on the list. International airports in Nice, Lyon, Bordeaux. Toulouse, and probably other places, though some parts of France are pretty handy to the Paris airports too.

London >> Belgium >> Amsterdam
Budapest >> Vienna >> Prague

Berlin could be worked in to a more rushed option of either plan.

On a couple of our trips to Budapest we layed over for a few nights in London, so that's a possibility. Depends on what carrier serves your home airport. Sounds like DFW, so that would be American/BA which means London is a real good possibility along with Prague, Vienna and Budapest.

Look at an open jaw into London and out of Budapest and then check out RT to London and using european discount carriers to get to Prague and then from Budapest back to London.

In July, I prefer to take advantage of those areas of Europe that are only good in the high summer months. Scandinavia is one of those areas, another is the north coast of Spain. Coastal areas tend to stay relatively cool but inland can get really hot (conversely coastal areas don't get as cold as inland in winter either).

I toured Baltic capitals one July/August and was happy to be there at that time of year. In St. Petersburg, however, it was well into the 90's and quite hot. Our guide said they have two seasons in St. Petersburg, July and winter (I'm sure August is nice too).

There's another random list from AbhinavSharma with no supporting comments. Do you just throw darts at a board, or do you want to give some reasons behind the suggestions?

Yeah, I'd certainly like to see a good reason why Istanbul would be one of the "best places to visit in July in Europe".