In Congress, each state gets two Senators in the Senate and Representatives in the House of Representatives based on population. Why would this aspect of the USA government make the North and South cautious of a new territory becoming a state?

They were worried about overrepresentation.

Explanation:

The North and the South were both anxious about adding new states on either side in worry that this would disrupt the equal balance of Northern and Southern Senators. Somewhat of a modern example would be the Republican worry of D.C. statehood overrepresenting Democrats.

no, to many things have came in to factor

the group i'm selecting: greeks.

a first group of greek immigrants came to the us in the 1850s. the second group came to america starting in the 1890s due to economic opportunities they didn't have back in their home caused by the hardships of ottoman rule. greek immigration was 90% male, many of them expected to work and return to greece after earning enough capital, but ultimately had to remain in the us after the greek genocide.