If you come from a school that only offers two years, you won’t be penalized for having 2. However, the expectation at top schools is Level4 or AP. Level 3 is basically the lowest they’ll look at. At UC’s they’ll chuck your application if you don’t have 2 years, but realistically if your school offers more and you’re applying to UCB, UCLA, UCSD, and even UCSB, taking 2 years when your school offers 4 will need something pretty exceptional to be seen as okay.
(Keep in mind that foreign language is a “marker” of academic ability or intellectual curiosity, just like Math is.)
You may, during senior year, double up in science instead of taking level 4 in a language, but even if yo’ure a “well-lopsided” student, if you don’t have the basic foreign language level (2 for UCs, 3 for other top colleges), it’s as if you were a teenager stating “Well, I can add and subtract and draw circles, and I want to major in Literature, so why should I take Algebra1, let alone Algebra2?”
What are the odds that kid would get into a very to highly selective 4-year college?
The answer to the question above is triple, by the way: first, because it stimulates different parts of your brain, that you need to make it function at top level; second, because the goal of education is to have an educated person, and acquiring knowledge in a variety of areas is indispensable to being educated; third, because colleges want students who display intellectual curiosity, find learning “cool” or can at least get over the idea they should only study if they like what they’re learning, students who can push through the boredom and still excell.
However, you may look for colleges that do not require foreign language proficiency (or a low level of it) for college graduation requirements.