Ok so if Spain was suddenly a US state it would be the biggest in population and 3rd biggest in terms of the economy (behind CA, TX and NY).
However, Spain would also be the poorest state, slightly behind even Mississippi. It would also have the biggest unemployment rate and it would not even be close.
Politically, Spain would be Safe D, ranging somewhere between 65-35 to 75-25 for Democrats. If you however adapt the parties to be more palatable to a Spanish audience, it would be a country that is a tossup; though a lot depends on how Catalan/Basque nationalists vote. However I will assume they side with the left of centre party and therefore Spain would still be very likely left. However the right would have a very high floor, just with a very low ceiling too.
Ironically Spain would be a very elastic place too as the country is not as polarized as the US. No 80% R or 80% D counties.
Spain would be entitled to a ton of Electoral votes too, probably something like 60 EVs? Still safe Biden in 2020.
In the Senate, Spain would have elected 2 Democrats. Although Spain might have elected a "RINO" of sorts in 2012 back when our left was 100% discredited.
As for the House, I actually drew a hypothetical "Spain as a US state" map not too far ago! Though I did use Spanish parties for it. It also has some high deviations as I priorized keeping autonomous communities whole.
In any case, here is the map (not pictured are the 3 Canary Islands seats):
https://www.google.com/maps/d/edit?mid=1F18ykvWXvJ3ouQ5LI1KIQya0pjRMc_5r&usp=sharingAnd here is the full list of seats:
Spoiler alert! Click Show to show the content.
A Coruña: Left
Santiago de Compostela: Tossup, tilt right
Vigo y Pontevedra: Left
Lugo y Ourense: Right
Asturias: Left
Cantabria: Right
Ávila, Salamanca, Zamora y El Bierzo: Right
Valladolid, Segovia y Soria: Right
León, Palencia y Burgos: Right
La Rioja: Right
Bilbao: Nationalist
Guipúzcoa: Nationalist
Álava-Encartaciones: Tossup, tilt left
Navarra: Left
Zaragoza: Right
Aragon: Right
Girona: Nationalist
Lleida: Nationalist
Tarragona: Nationalist
Penedés: Nationalist
Anoia-Vallés Occidental Nord: Tossup, tilt nationalist
Barcelona Nord - Vallés Occidental Sud: Tossup, tilt nationalist
Baix Llobregat: Left
Barcelona Centre: Nationalist
Barcelona Nord: Left
Badalona - Maresme Oest: Left
Menorca - Pla de Mallorca: Left
Palma de Mallorca e Ibiza: Left
Castellón: Tossup, tilt left
Norta Noroeste: Left
Valencia: Right
Ribera del Turia: Left
Marina de Alicante: Left
Alicante: Right
Elche y Torrevieja: Right
Alcobendas y Alcalá de Henares: Right
Guadarrama: Right
Cuenca del Henares: Left
Getafe, Leganés y Fuenlabrada: Left
Móstoles y Alcorcón: Tossup, tilt right
Madrid Southeast: Left
Madrid Southwest: Left
Madrid Centre: Right
Madrid North: Right
Madrid East: Right
Toledo: Right
Ciudad Real y Albacete: Right
Guadalajara y Cuenca: Right
Cáceres y Mérida: Right
Badajoz: Right
Murcia: Right
Cartagena: Right
Huelva-Sierra Oeste: Left
Aljarafe: Left
Sevilla: Left
Lower Guadalquivir: Left
Cádiz: Left
Córdoba: Right
Jaén: Right
Campo de Gibraltar - Costa del Sol: Right
Málaga: Right
Sierra de Málaga - Costa Tropical: Right
Granada: Right
Almería: Right
Gran Canaria East: Left
Tenerife South: Left
Rest of the Canaries: Left
Total numbers would be:
24 Left seats
2 Tilt left seats
30 Right seats
2 Tilt right seats
7 nationalist seats
2 Tilt nationalist seats