In the US, the first thing you choose is the carrier, based on coverage where you need coverage. So see whicvh, if any, carrier has coverage where you need coverage and that your phone can operate on. Then use that carrier while you're n the US.
Sticking strictly to one carrier, for whatever reason you have for sticking to TMobile, may guarantee you no coverage whatsoever where you'll be. (There's an entire village near where I live that has absolutely zero signal from AT&T - they won't fix it because they'd get almost no customers even if they did, so it would be a wasted investment for them.)
So either you choose a different carrier, or you stay with poor-to-no coverage. Most carriers cover large college towns solidly, and you're not that far from DC, Silver Spring, Chevy Chase, Bethesda - areas that should have good coverage - from some carrier, at least. The problem is that the European version of the C41 is missing at least 2 bands (4 and 12) that would give you better coverage here.
You may find that, in order to get decent coverage here, you can't find any carrier that will work with your phone and you'll just have to buy another phone for use while you're here. (If it's for 4 years, it would pay to get a good one, because even a flagship phone isn't worth that much after 4 years - a cheap phone would be worth almost nothing. But if you're going to be here for a short time, you may be able to get away with a cheaper phone, and get some of the money back by selling it before you leave.)
(As for ditching 2G, 3G will handle it. My 5 year old Note 3s, that still have the hardware and software for 2G voice and text, run perfectly well on AT&T - that switched to 3G over 2 years ago.)