Is it permissible to delay giving out zakat until traveling to the zakat payer's country, and then giving it to the imam of the mosque in the country of residence to dispose of it, or sending it to a needy widowed woman in the zakat payer's country?

If the Imam is trustworthy and knowledgeable about the disbursement channels of Zakat (definition), and he pays it to its deserving recipients within the same country where the wealth is located, then it is preferable to appoint him as an agent for its distribution, to avoid the dispute of those who prohibit the transfer of Zakat, even though the preponderant opinion permits its transfer out of need. However, if he will distribute it outside the country, then you have the choice between appointing him or appointing your sister to give it to the deserving woman, while ensuring that she is among the deserving poor.