So say that Franco is convinced to join the Axis and declares war on the Allies in late 1940, leading to the fall of Gibraltar and a tougher Med campaign. Obviously the Axis is still going to collapse, and maybe by 1943 Spain itself will have been partially invaded ala Italy, while the Third Reich and its Axis allies collapse is all but assured by 1945 still. However, with Franco having willfully joined the Axis, does he get to remain in power? Will the Allies simply overthrow Falange? Who could even govern Spain in the aftermath.
As a bonus, do we see a civil war like post-war Greece between resurgent Republicans and Monarchists?
Just to talk about the current state of spain in the late 1930s/early 40s to show how little this changes anything apart from maybe an extra year taking spain max,
Spain is in debt to Germany (and iirc Italh to a more limited extent) after their support during the civil war
Industry and cities are bombed out
People are jobless due to the previous statement
The economy is just starting to recover
Their army likely couldn't fund or support much in terms of military operations, with Gibraltar and some incursion into the Mediterranean by marines (most likely Operation Hercules as the threat of the royal navy is no longer holding an invasion of malta back)
And finally AMERICA
Afterwards,
Franco is defeated and spain occupied by late 1943-mid 1944
We may see a split of spain if the leaders of the west and east are as high as they were when making border proposals for splitting nations, but it's unlikely
A republic and potentially authoritarian one (maybe even a military dictatorship) is set up with western collaborators
There's a chance spain gets swooped up in the Marshall Plan
And spain would take about a decade longer to financially recover by entering ww2
Long story short they stand no chance the british and american industrial capacities and manpower would crush spain into paste and there are several easy points to invade from