I am applying to a couple T20 schools, but I noticed many top schools recommend 3+ years of the same foreign language. I have only 2 years worth of foreign language classes. I placed out of our Mandarin I course and completed Mandarin II and III - the highest level offered.
Will this have an impact on my application? If so, should I look into enrolling in another foreign language course? Senior year has already begun for me, so doing that would be a bit difficult.
You completed level 3, so that counts as 3 years. If your school’s curriculum stops at level 3, then not having level 4 won’t be counted against you. Another year in a different language is a waste of time. If you really want to continue Chinese, you can see if any nearby community colleges offer, but it won’t be a make or break
If you have completed Mandarin 3, that is the equivalent of 3 years even if you only took the last 2.
In terms of whether Mandarin is “foreign enough”, I might mention one personal example. I am originally from Montreal. The only “foreign” language that I ever studied was French. At least one “top 10” school in the US thought that French was foreign enough for them, even though it is not really “foreign” at all for anyone from Montreal.
I think that it is too late to do anything other than apply and see what happens. Also, my best guess is that you will be fine. Of course, admissions to any Top 20 university is always unpredictable and a reach.
Make sure your GC includes in their HS profile that the highest level of Madarin offered is III. This way they know you took the highest level offered.