The republican party is not the Whig party, it just got a lot of it’s members.
Correct. The only common attribute of the Republicans in the late 1850's when the party was formed was the opposition to the expansion of slavery into the Western territories.
There were abolitionists involved, but they were a small minority. There were old time 'internal improvement' Whigs involved, but they were also a minority. There were protective tariff interests involved, but they were also a minority. The only common theme was opposition to slavery expansion.
Whig politicians, North and South, tended to favor both internal improvements and protective tariffs, but were wildly split on the issue of the expansion of slavery.
That fundamental division inside the Whig party is what killed it. The pro-slavery/expansionist Whigs became Democrats while the anti-expansionist Whigs became Republicans.
I don't know if it is immigration policy or Federal spending --- but I'm sensing divisions in the Republican party today that could echo the Whig divisions of the mid 19th century.