You should use
The Diccionario Panhispánico de Dudas (DPD) warns that the construction a + infinitive is not natural to Spanish:1 it's a syntactic structure that was introduced from French language and became popular around the XIX century (I'm guessing, due to bad translations at the height of French romanticism). So, you must be very careful when using it. The DPD suggest the following:
a) Si la preposición
a admite su sustitución por las preposiciones
para, o el relativo
que, [...] debe desecharse la construcción galicada.
a can be replaced with
que, [...] one must dismiss this French structure.
Now, let's see if we can use
para in the sentence without changing its meaning (if true, as stated in the DPD, we must dismiss
The campaign to ratify USMCA.
In the original sentence, the preposition
to is marking a "purpose" relation between two elements:
The campaign and
ratify. You can think of it as this way: In order to get the USCMCA ratified, there was a campaign.
Now, according to the Nueva Gramática Española (something like the official Spanish grammar manual), 2 in Spanish there's only one preposition that conveys that purpose relationship:
La campaña para ratificar el USMCA.
para is better suited than
a, as the DPD's rule states, we must dismiss
a and stick to
Small tip: prepositions are tricky when learning a new language. Even natives often have problems! This is because, unlike other words like verbs, adjectives or nouns, prepositions do not have a fixed lexical content (i.e., their meaning is always changing). They're relational words: their meaning changes when their position in a sentence changes. For example, the may work in one way when they're in front of a noun, but in another when they're in front a transitive verb, or when they introduce an indirect object, etc. Therefore, it's a bad practice to assign prepositions in your target language a preposition in your native language (
to is not always
a is not altwas
1. As well as the construction noun + a + noun.
2. p. 569.