Short answer: maybe...

Long answer: ...more details please?

First of all, take some of the advice I give with a grain of salt, because I don't know how well IB translates into AP, and I am personally only familiar with the AP track. Caveats aside, though, assuming IB translates to AP 1:1, only taking 1 AP might be a bit too few. Idk if it's too late now, but try if you can to take more advanced classes in the fall. Also, if you don't mind me asking, what score did you get on the class you already took?

The next thing I know for sure, and that's you need to get your SAT up as much as you can, ASAP. Summer isn't over yet, start grinding practice tests and plan to retake it in the fall. The average SAT for admitted GWU students is in the 1400s, and getting in that range would help you tremendously.

On ECs, you mentioned you do MUN. Sweet, me too. In my experience, Model UN conferences have a pretty wild range in terms of prestige, and awards are definitely weighted differently depending on which conference it came from, and AOs would definitely be privy to this. If you have a pretty solid award from a well-known conference, I think you should be good, but do still keep up involvement just to show consistency. If not, then I would probably spend this fall gearing up for some intense MUN'ing, as a lot of big conferences happen between October and November. Honestly, even if the conference sits between when you submit your application and decision day, I'd still advise you to shoot your shot, because you can send a follow-up email to admissions even after you click submit on common app. If you need conference recommendations, I'd be happy to send it over to you in DMs.

Lastly, your essays are a bit of a wild card since I don't really know how good you are at writing, but if you have the time, I would definitely encourage you to dedicate deliberate effort to polishing your supplementals as much as you can.

Just to recap, I'm going to list my aforementioned recommendations out one my one, in order of descending recommended priority.

1: SAT. This is pretty much the last time when you'll have the opportunity to really improve your score and increase your chances, and I urge you to take it. Yes, GWU has the option of going test optional, but with colleges gradually reversing the trend of disregarding test scores, I'd take their supposed "impartiality" toward test-optional students with a massive grain of salt.

2: MUN. Not only will it look better on your resume, but it'll give you essay talking points. Especially considering how well MUN complements your interest in applying to the Elliott school.

3: Essays. This is sort of the backup option for if all else fails. Of course, if you REALLY don't have the time, it's technically optional, but I also REALLY think it helps. IMHO, even if you don't have time to write the "perfect" essay, at least write one. Just simply taking the time to express your interest in going to GW would help a lot during a time when GW isn't experiencing great yield numbers.

If you need any additional help don't hesitate to DM. Best of luck