Not irrational at all! (I’m speaking to study abroad, not a gap year, which is up to you, if you can find the right program.) Please pursue this opportunity, especially if your’e interested in IR. Look for schools that will maintain your level of financial aid if you decide to study abroad – a lot of schools will do that, especially those where a majority of students spend some time abroad. Ask if they’ll cover extra expenses (books, transportation back and forth to the US) as well – some will for students on need-based aid. There are many year-long programs, but I think it’s more typical to do a semester, because the courses you take abroad don’t always count toward your major. So not everyone can afford a whole year. For the most flexibility, look for schools that don’t limit you to their own study-abroad programs but will allow you to join a different institution’s program (I think probably most schools allow this).
There are also a few schools for which your tuition for a semester abroad will be based on the costs at the school you’re visiting (not the school you usually attend). That’s almost sure to be a lot less expensive. For example: my D attends Bates and is abroad this semester. Our costs are about 75% of what they normally would be, and that includes tuition, housing, transportation, and all fees. Not all schools do that (some just charge the usual tuition), but it’s worth asking how study abroad will work financially at any school you’re considering.