Does Customs ‘warning’ Fall Under Criminal Offence/convictions?

I flew to USA for the first time & got caught in the classic “I forgot to declare the airline sandwich” scenario with the customs and the cute beagle. My sleepy brain did not see nor register the lettuce in the sandwich as the vegetable. I am normally very careful with customs and my first time ever getting into trouble with customs. The customs officer told me to declare them next time, noted down my passport details, but did not fine me or charge me with anything. My question is just the title. Does it fall under criminal offence? Do I have to declare it under criminal offence or convictions in government documents such as visa applications? What are the complications from this? Would I be in high alert category for customs (i.e. pulled over everytime) in other countries (e.g. Australia they share some info??). Sorry if these are dumb questions. No luck finding specific info anywhere else. Thanks in advance