too much in one month?

Doesn't sound overly ambitious to me...especially since you say you're young and energetic.

I also think it seems OK. In fact, you could consider squeezing Bratislava in between Vienna and Budapest. You can hop on a boat in Vienna that zips down to Bratislava, which is worth a quick visit, including a side trip to the ruins of Devin Castle. From Bratislava, there are a number of trains to Budapest.

Usually when someone asks if they are packing in too much, they share a crazy overly ambitious plan with no time for travel - so it is very refreshing to see a reasonable plan!

Be sure to book your flights using the "multi-city" option. I also recommend sketching out what you want to see and do in each stop to determine if you have the right number of nights in each city. Consider day trips from these bases to add in some non-city time.

Enjoy the trip!

Just remember that your first day in Europe and your last day in Europe will essentially be wasted days getting into the city and getting to the airport. Then, every day you move from one city to another will be a lost day.
Technically, your itinerary is possible. In reality, I'd be worn out after the third city following your schedule. But every city you're going to is an absolutely great European city worthy of more time.
We just returned from Rome and Budapest. I cannot think of any more lively place than Budapest on a June night of running the Ruin Pubs--Honkey Tonk Heaven. Millennials are everywhere.

The itinerary looks good.

As a general rule, I prefer daytime travel (I am no longer young and energetic enough for night trains), arriving at my destination during the afternoon or early evening, so it's easier to take public transportation to my hotel rather than a more expensive taxi.

This dorsn't appear too ambitious to me. Enjoy your travels!

Only thought I have is to maybe put your Alps visit before entering Italy to avoid backtracking.

Go for it just make sure you take some rest days to recover from the travel between places

This is the rare post with a positively nice travel plan - you've set it up very nicely! Enjoy and congratulations on finishing your undergrad!

Not overly ambitious at all and I expect you'll have an amazing trip! Well done!

This travel itinerary is actually quite an educated plan. I cringe when I read itineraries like: "I have 24 hours in Venice so I want to visit Murano, Burano, Torcello and maybe Padua" AArrggghh

Don't know why people travel thousands of miles to a destination and spend their few hours there trekking to outlying areas.

Congratulations on being SMART!