The American P2 kids are clearly weaker on my favourite maths foundation skills (see eg below), but some of them go on to become good maths students. At P2

Some of them are probably careless, lacking the rigorous training in China.

Some of them are perhaps slow with pattern recognition in academic maths problem solving.

Some of them probably lack the number familiarity, that comes from lots of practice with numbers.

Now I don’t know what kind of maths skills must be developed at an early age and really can’t wait. Multiplication verses? Subtraction within 20?

Outside maths, pinyin is another foundation skill but I feel it too can be learnt later, though it’s much better to get a firm grip early on.