The loud music would draw a political rebuke / protest response, and then after if it didn't cease, it would plausibly draw some kind of tit for tat response in the other nation. The US can expel diplomats and isolate an embassy (eg cut power, water, etc), essentially making it non-maintainable (inhospitable) as a position. It could also surround it literally, effectively sealing it off to access, preventing the ability to leave (with predictable consequences).

The strong microwaves would be treated as an act of war: an attack on Americans, on American soil, by a foreign power. If it didn't immediately stop, the US would invade that foreign soil and do whatever it decided was required.